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Stereoselective sulfation of terbutaline by the rat liver cytosol: evaluation of experimental approaches
Author(s) -
Walle U. Kristina,
Walle Thomas
Publication year - 1989
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.530010205
Subject(s) - sulfation , chemistry , enantiomer , cytosol , terbutaline , substrate (aquarium) , stereoselectivity , enzyme , sulfotransferase , chromatography , stereochemistry , biochemistry , catalysis , medicine , oceanography , asthma , geology
Abstract Little is known about the stereochemistry of sulfation of chiral phenolic drugs. In this study we examined several in vitro approaches to this question, using (+)‐, (−)‐, or (±)‐terbutaline as the substrate and the rat liver cytosol as the phenolsulfotransferase enzyme source. The cosubstrate PAPS was either generated by the cytosol from inorganic sulfate and ATP or added to the cytosol. The intact sulfate conjugates formed were determined by HPLC. Using the PAPS generating system, which is best suited for the production of relatively large quantities of sulfate conjugates, with the individual enantiomers as substrates, (+)‐terbutaline was conjugated to a much greater extent than (−)‐terbutaline; the (+)/(−)‐enantiomer ratio was 7.3 ± 0.3 (mean ± SE). When (±)‐terbutaline was the substrate and chiral derivatization was employed to separate the sulfate enantiomers formed, a similar (+)/(−)‐enantiomer ratio of 7.9 ± 0.2 was obtained. With PAP 35 S added to the cytosol, an approach best suited for kinetic studies, the substrate concentration dependence of sulfation could be determined. The K m app for this reaction was identical for (+)‐ and (−)‐terbutaline. However, the V max app was 8.1 ± 0.4 times greater for (+)‐terbutaline. This study for the first time shows enantioselectivity in sulfation of a chiral phenolic drug. The experimental approaches used should be valuable for human studies of stereoselectiven sulfation of terbutaline and other chiral drugs.